This invention relates generally to a method and apparatus for data compression and, in particular, to a novel method and apparatus for reducing the number of bits of information needed to transmit a video image by using a technique which generates symbols from bands of data taken from the original image.
In the transmission of digital data, it is desirable to reduce the data to be transmitted as much as possible in order to reduce the bandwidth requirements of transmission medium and storage requirements. One technique which has proven useful in compacting digital image data is known as run length encoding. This particular technique consists of partitioning each row (scan line) of the image or array into a sequence of runs, with each run (including one or more adjacent picture elements, called pixels, with the same binary value, and representing each run with a symbol or code which specifies the length of the run. Often, these symbols are represented by variable length codes, such as a Huffman code set, and are assigned such that the shorter code words are used to represent the symbols which are more likely to occur, and the longer code words are transmitted for symbols which rarely appear.
However, it is possible to employ the run length concept in a different manner to develop a novel scheme for achieving improved data compression performance. This novel scheme is combined with an additional technique which groups together binary representations of different symbols, formed from data elements, to devise a different approach to efficient data compression.